Irrigation leads to new Se-toxicity paddy fields in and around typical Se-toxicity area.

Although the issue has been of much concern and has subsequently been controlled for years, the environmental risk of excess selenium (Se) in farmlands still has not been eliminated in Se-toxicity areas. Different types of farmland utilization can change Se behavior in soil. Thus, located field monitoring and surveys of various farmland soils in and around typical Se-toxicity areas spanning eight years were conducted in the tillage layer and deeper soils. The source of new Se contamination in farmlands was traced along the irrigation and natural waterway. This research indicated that 22 % of paddy fields increased to Se-toxicity in surface soil led by irrigation with high-Se river water. Selenate is the dominant Se species in rivers (90 %) originating from geological background areas with high Se. Both soil organic matter (SOM) and amorphous iron content played important roles in the fixation of input Se. Thus, available Se was increased by more than twofold in paddy fields. The release of residual Se and eventual bounding by organic matter is commonly observed, thus suggesting that stable soil Se availability seems sustainable for a long time. This study is the first report in China that shows how new soil Se-toxicity farmland is caused by high-Se water irrigation. This research warns that external attention should be paid to the selection of irrigation water in high-Se geological background areas to avoid new Se contamination.

Selenium distribution in the Chinese environment and its relationship with human health: A review.

This paper reviewed the Se in the environment (including total Se in soil, water, plants, and food), the daily Se intake and Se content in human hair were also examined to elucidate Se distribution in the environment and its effects on human health in China. Approximately 51% of China is Se deficiency in soil, compared with 72% in the survey conducted in 1989. Low Se concentrations in soil, water, plants, human diet and thus human hair were found in most areas of China. The only significant difference was observed between Se-rich and Se-excessive areas for Se contents in water, staple cereal, vegetables, fruits, and animal-based food, no remarkable contrast was found among other areas (p>0.05). This study also demonstrated that 39-61% of Chinese residents have lower daily Se intakes according to WHO/FAO recommended value (26-34µg/day). Further studies should focus on thoroughly understanding the concentration, speciation, and distribution of Se in the environment and food chain to successfully utilize Se resources, remediate Se deficiency, and assess the Se states and eco-effects on human health.

Risk assessment for human health in a seleniferous area, Shuang'an, China.

Shuang'an in Ziyang is a typical high-selenium (Se) area in China, where human selenium (Se) poisoning was reported 30 years ago. To assess the risk of Se poisoning in the area, the Se content in agricultural soil, plant, and water in Naore, Shuang Hekou, and Lin Benhe villages of Ziyang was systematically investigated. The probable daily intake (PDI) was calculated on the basis of Se contents in food, water, and dietary habits to evaluate the risk of selenosis. Se content in hair from local habitants (32 men and 34 women) was determined to further verify the risk. Results showed that Se content in the soil ranged from 0.21 to 36.07 mg/kg, with a geometric means of 3.02 ± 5.16 mg/kg, respectively. Approximately 60% of soil reached the Se toxicity threshold (>3 mg/kg). The Se content in plants ranged from 0.02 to 17 mg/kg, with an average of 0.76 ± 2.51 mg/kg. Approximately 40% of the plant reached the toxicity standard (1 mg/kg). Se content in soil and plant of Naore village was significantly higher than that from two adjacent villages. The Se content in vegetables (on fresh weight basis) was higher than that in cereals. Se contents were 3.73 ± 9.08 and 1.32 ± 3.50 mg/kg in eggplant and pepper, respectively. The Se content in drinking water was 7.85 ± 6.04 µg/L, lower than the upper tolerable limit (40 µg/L) set by WHO. The Se content in stream water (18.5 µg/L) was significantly higher than that in drinking water because of soil erosion. The calculated PDI of habitants in Naore village (1801 µg/day) was significantly higher than that in Lin Benhe (666 µg/day) and Shuang Hekou (686 µg/day), all of which was higher than the tolerable upper Se intake (400 µg/day) set by WHO. The calculated blood Se content was relatively high, especially for habitants of Naore village (2783-2824 µg/L). Moreover, the Se content in the hair of local habitants reached as high as 12.72 ± 13.81 mg/kg, and 78.79% exceeded hair Se toxicity threshold (>3 mg/kg), which further verified the potential selenosis risk. Our study provides significant implications of the potential Se intoxication of local residents. Therefore, governments and other institutions should implement various measures to reduce the daily Se intake and to mitigate the associated health risks.

[Effects of Nitrogen Application on Selenium Uptake, Translocation and Distribution in Winter Wheat].

In order to better understand the effects of nitrogen application on accumulation, translocation and distribution of selenium in winter wheat and to provide theoretical reference for reasonable nitrogen application and increasing selenium content of grains. A pot experiment was carried out under greenhouse conditions with Se1 (0.74 mg·kg-1) or Se2 (2.60 mg·kg-1) levels of selenium, and each Se treatment was supplied with N1 (100 mg·kg-1) or N2 (200 mg·kg-1) levels of nitrogen, respectively. Selenium concentrations and biomass amounts of different parts of wheat were determined at jointing and maturity stage. The results showed that grain yield increased with increasing nitrogen levels by 13.2% and 24.0% in Se1 and Se2 treatment, respectively. Regardless of N rate, Se concentration of wheat increased with raising Se amended rate (P<0.01). Increasing nitrogen application could promote Se uptake of root and thus increase the selenium concentration of wheat grains and leaves, which was greater in Se1 treatment than in Se2 treatments. Se concentrations in wheat grain increased by 22.6% and 12.1% with the increasing N application rate in low and high Se treatment, respectively. The distribution ratios of Se in each organ ranked the same as BCFs, following the order of leaf > grain > glume > root. Increasing N fertilization increased the distribution ratio of Se in grains by 11.1% and 25.9% in low and high selenate treatments, respectively. High nitrogen fertilization could promote uptake and translocation of Se in wheat under low Se conditions, and improve Se use efficiency as well in the agricultural production.

Human health risk assessment of heavy metals in the irrigated area of Jinghui, Shaanxi, China, in terms of wheat flour consumption.

Contamination of heavy metals (HMs) in agricultural soil has become a serious environmental problem because it poses a serious threat to human health by entering into food chains. Wheat is a staple food of the majority of the world's population; therefore, understanding the relationship between HM concentration in soils and its accumulation in wheat grain is imperative. This study assessed the concentrations of HMs (i.e., Hg, As, Cd, Cr, Pb, Cu, Zn, and Ni) in agricultural soils (a loess soil, eum-orthic anthrosol) and wheat flour in the historical irrigated area of Jinghui, Northwest China. The potential human health risks of HMs among local residents were also determined by evaluating the consumption of wheat flour. Results showed that the mean soil concentrations of HMs exceeded the corresponding natural background values of agricultural surface soil in Shaanxi: 0.07 mg kg(-1) for Hg, 15.4 mg kg(-1) for As, 0.25 mg kg(-1) for Cd, 75.5 mg kg(-1) for Cr, 27.2 mg kg(-1) for Pb, 28.1 mg kg(-1) for Cu, 81.1 mg kg(-1) for Zn, and 36.6 mg kg(-1) for Ni, respectively. However, all of the mean concentrations of HMs in soil were within the safety limits set by the Chinese regulation (HJ332-2006). The total HM concentrations in wheat flour were 0.0017 mg kg(-1) for Hg, 0.028 mg kg(-1) for As, 0.020 mg kg(-1) for Cd, 0.109 mg kg(-1) for Cr, 0.128 mg kg(-1) for Pb, 2.66 mg kg(-1) for Cu, 24.20 mg kg(-1) for Zn, and 0.20 mg kg(-1) for Ni, and they were significantly lower than the tolerance limits of Chinese standards. However, 15% of the wheat flour samples exceeded the Chinese standard (GB2762-2012) for Pb. This study highlighted the human health risks in the relationship of wheat flour consumption for both adults and children with HMs accumulated area. HMs did not cause noncarcinogenic risks in the area (HI < 1) except for children in Jingyang county; Cd generated the greatest carcinogenic risk, which poses a potential health risk to consumers. The results obtained in this study showed that the government and other institutions should implement measures to prevent and control HM contamination in agricultural soil and crops to mitigate the associated health risks.

Selenium geochemical distribution in the environment and predicted human daily dietary intake in northeastern Qinghai, China.

Ping'an is a selenium (Se)-rich region located in northeastern Qinghai Province of China. To better understand the selenium geochemical distribution and its potential ecological effects, this field study investigated the Se distribution in the local environment, soil Se bioavailability, and the daily dietary Se intake of Ping'an residents. Concentrations of total Se were determined in soil, plant, water, and food samples. Results showed that Ping'an is generally a Se-rich region in China. High-Se soil mainly distributes in the north of Hongshuiquan Town in the study region. Se concentration in 43 plant samples varied significantly from not detected (nd) to 904 µg/kg, following a descending order of pasture > grain > vegetable > fruit, which was much lower than other regions in China. The drinking water Se concentrations were also significantly lower than the European and Chinese surface water Se standards of 10 and 50 µg/L. The predicted daily dietary Se intake (48 ± 20 µg per person) in Ping'an met the demand of the WHO-recommended Se amount of 55 µg per person. The Se content is high in soil, but low in different kinds of plants and Se intake, indicating that Se that can be taken up by plants was very low. The K2HPO4-KH2PO4-extractable Se in the soil accounted for only 3% of the total soil Se, indicating that a low soil bioavailable Se might result in low Se accumulation in plant tissues in Ping'an. This might be due to the influences of geochemistry and the inherent properties of the parent materials of these soils. Therefore, further studies need to focus on better understanding the process and influential factors to soil Se bioavailability to successfully utilize the soil Se resource in low-Se-availability areas.

Suitable depth of epidural puncture in nulliparous pregnant woman.

We study the suitable depth for epidural puncture in primiparas so as to decrease epidural complications and provide anesthesiologists with an appropriate insertion guide. A prospective study of 87 primipara patients receiving labor analgesia who had epidural punctures in the course of vaginal delivery were randomly divided into 3 groups: the L 3,4 group (N = 27), the L 2,3 group (N = 29), and the L 1,2 group (N = 26). Predictive statistical models were used for the formulation of the ideal epidural puncture needle depth. Eighty two patients who had non-traumatic epidural punctures were studied. There were no significant changes in age, weight, height, weight/height ratio, gestational weeks, fetus weight, pregnancy weight, weight difference, and fetus weight (P > 0.05). Compared with L 3,4 intervertebral space, the puncture depth in L 1,2 and L 2,3 was significantly shorter (P < 0.05) and (P < 0.001), respectively; Regression equation: PD (cm) = 0.351 [LHZ] + 0.147 [BMI] + 0.017. The correlation coefficient for LHZ was 0.351 (95 % CI 0.278-0.424; P < 0.001), the correlation coefficient for BMI was 0.147 (95 % CI 0.123-0.171; P < 0.001). This formula is accurate and practical with less complex calculations. However, further validation through a prospective study will be required. It is an accurate way to localize the puncture site in parturients and improve the efficiency of puncture in parturients for analgesia labor.Epidural puncture depth prediction in L 1,2, L 2,3, and L 3,4 can supply with a related reference.

Transformation of heavy metal fractions on soil urease and nitrate reductase activities in copper and selenium co-contaminated soil.

This study aims to explore the effects of the distribution, transformation and bioavailability of different fractions of copper (Cu) and selenium (Se) in co-contaminated soils on soil enzymes, providing references for the phytoremediation of contaminated areas and agriculture environmental protection. Pot experiments and laboratory analysis were used to investigate the transformation and bioavailability of additional Cu and Se for pakchoi (Brassica chinensis) in co-contaminated soil. In the uncontaminated soil, Cu mainly existed in residual form, whereas Se was present in residual form and in elemental and organic-sulfide matter-bound form. In the contaminated soil, Cu mainly bound to Fe-Mn oxidates, whereas Se was in exchangeable and carbonates forms. After a month of pakchoi growth, Cu tended to transfer into organic matter-bound fractions, whereas Se tended to bound to Fe-Mn oxidates. The IR (reduced partition index) value of Cu decreased as the concentrations of Cu and Se gradually increased, whereas the IR value of Se decreased as the concentration of Se increased. The IR value before pakchoi planting and after it was harvested was not affected by the concentration of exogenous Cu. Soil urease and nitrate reductase activities were inhibited by Cu and Se pollution either individually or combined in different degrees, following the order nitrate reductase>urease. The significant correlation between the IR value and soil enzyme activities suggests that this value could be used to evaluate the bioavailability of heavy metals in soil. Path analysis showed that the variations in exchangeable Cu and organic-sulfide matter-bound and elemental Se had direct effects on the activities of the two enzymes, suggesting their high bioavailability. Therefore, the IR value and the transformation of metals in soil could be used as indicators in evaluating the bioavailability of heavy metals.